Obesity Raises Risk of Delayed Renal Allograft Function

Obese patients who undergo kidney transplantation are at higher risk of delayed graft function (DGF) than non-obese patients, but they have a similar risk of graft loss and death, according to Brazilian researchers.

Gabriela C. Souza, PhD, of Hospital de Clínicas de Porto Alegre in Porto Alegre, and colleagues conducted a systematic review and meta-analysis of 21 studies that included a total of 9,296 patients who received a kidney transplant.

Obese patients had a 41% increased risk of DGF and a twofold increased risk of cardiovascular disease death compared with non-obese patients. An analysis of studies published before 2003 showed that obese patients had a 65% increased risk of death at 1 year post-transplant.

The researchers found no association between obesity and the risk of death at 1 year post-transplant in studies published after 2003. The study revealed no association between obesity and acute rejection.

“The association of obesity with DGF may be related to immunologic and nonimmunologic factors,” the investigators wrote in a paper published online ahead of print in Transplantation. “Obesity is associated with a proinflammatory environment, with elevated levels of cytokines and chemokines that can mediate the immunologic responses and facilitate DGF.”

In addition, technical difficulties encountered while performing a transplant operation in obese patients may lead to a more pronounced ischemia-reperfusion injury and thus an elevated risk of DGF.

“Obesity should not on its own preclude a patient from being considered for kidney transplantation,” Dr. Souza's group concluded.

For the study, the investigators defined obesity as a body mass index of 30 kg/m2 or higher.

In a study published in Kidney International (2011;80:218-224), researchers led by Kamyar Kalantar-Zadeh, MD, MPH, PhD, now with the University of California Irvine, reported on a study showing that increasing pretransplant BMI is associated with an increasing risk of DGF.

Compared with renal transplant recipients who had a BMI of 22-24.99, those with a BMI of 25-29.99, 30-34.99, and 35 or higher had a 1.30, 1.42, and 2.18 times increased risk of DGF, respectively. The study included 11,836 hemodialysis patients who underwent kidney transplantation from July 2001 to June 2007.

A biologically plausible explanation is that obesity is associated with longer operative time and longer warm ischemic time, which are risk factors of DGF, according to the researchers. Another potential explanation is the link between obesity and increased pro-thrombotic activity and endothelial dysfunction.